Cancer Doctors Cite Risks of Drinking Alcohol

The American Society of Clinical Oncology, which represents many of the nation’s top cancer doctors, is calling attention to the ties between alcohol and cancer. In a statement published Tuesday in the Journal of Clinical Oncology, the group cites evidence that even light drinking can slightly raise a woman’s risk of breast cancer and increase a common type of esophageal cancer.

Heavy drinkers face much higher risks of mouth and throat cancer, cancer of the voice box, liver cancer and, to a lesser extent, colorectal cancers, the group cautions.

“The message is not, ‘Don’t drink.’ It’s, ‘If you want to reduce your cancer risk, drink less. And if you don’t drink, don’t start,’” said Dr. Noelle LoConte, an associate professor at the University of Wisconsin-Madison and the lead author of the ASCO statement. “It’s different than tobacco where we say, ‘Never smoke. Don’t start.’ This is a little more subtle.”

Other medical groups have cited the risks of alcohol as a possible cause of cancer. But this is the first time that ASCO has taken a stand.

Drinking over all, as well as heavy drinking and problem drinking, are on the rise in the United States and affect all segments of society, including women, older adults, racial and ethnic minorities and the poor, several surveys have shown.

Yet few adults, when asked, identify alcohol consumption as a risk factor for cancer, even though the vast majority were familiar with other cancer risk factors, like smoking and sun exposure, a recent ASCO survey of 4,016 adults found. Fewer than one in three adults identified alcohol as a risk factor for cancer. (Most also failed to mention obesity as a risk factor.)

The doctors’ group is also calling for new public health initiatives to curb alcohol use, from taxes to restrictions on ads targeting minors, like the new ban on alcohol advertising on New York City’s subways and buses slated to go into effect in January. The group likewise opposes “pink washing,” in which alcohol companies drape their products in pink ribbon to enhance sales, a practice it opposes “given the consistent evidence that shows the link between alcohol consumption and an increased risk of breast cancer.”

For the statement, ASCO researchers reviewed earlier published studies and concluded that 5.5 percent of all new cancers and 5.8 percent of all cancer deaths worldwide could be attributed to alcohol. The paper stated clearly that alcohol plays a causal role in cancers of the throat and neck, voice box, liver and colon, as well as esophageal squamous cell carcinoma and, in women, breast cancer.

For women, just one alcoholic drink a day can increase breast cancer risk, according to a report released in May from the American Institute for Cancer Research and the World Cancer Research Fund that was cited by ASCO. That report analyzed 119 studies, including data on 12 million women and over a quarter of a million breast cancer cases, and concluded there was strong evidence that alcohol consumption increases the risk of both pre- and postmenopausal cancer, and that drinking a small glass of wine or beer every day — about 10 grams of alcohol — increases premenopausal breast cancer risk by 5 percent and postmenopausal risk by 9 percent.

“The more you drink, the higher the risk,” said Dr. Clifford A. Hudis, the chief executive of ASCO. “It’s a pretty linear dose-response.”

Even those who drink moderately, defined by the Centers for Disease Control as one daily drink for women and two for men, face nearly a doubling of the risk for mouth and throat cancer and more than double the risk of squamous cell carcinoma of the esophagus, compared to nondrinkers. Moderate drinkers also face elevated risks for cancers of the voice box, female breast cancer and colorectal cancers.

The risk for heavy drinkers — defined as eight or more drinks a week for women and 15 or more a week for men, including binge drinkers — are multiples higher. Heavy drinkers face roughly five times the risk of mouth and throat cancers and squamous cell esophageal cancers than nondrinkers, nearly three times the risk of cancers of the voice box or larynx, double the risk of liver cancer, as well as increased risks for female breast cancer and colorectal cancer.

“If you look at these figures, you see alcohol is a contributing factor; certainly it has a causal role,” Dr. Hudis said.

The International Agency for Research on Cancer, which is part of the World Health Organization, first classified the consumption of alcoholic beverages as carcinogenic to humans in 1987, tying consumption to cancers of the mouth, throat, voice box, esophagus and liver, said Susan Gapstur, vice president for epidemiology at the American Cancer Society.

Since then, she said, more and more evidence has accumulated tying alcohol to a broader group of cancers, including colorectal cancer and, in women, breast cancer. A more recent I.A.R.C. report concluded that alcohol “is a cause of cancers of the oral cavity, pharynx, larynx, esophagus, colorectum, liver and female breast.” (The esophageal cancer is largely specific to squamous cell carcinoma.)

“The story of alcohol has been quite consistent and has been peeled away like an onion over time, and we’re continuing to learn more about the mechanisms involved,” Dr. Gapstur said. “We don’t have randomized trials, but sometimes when you start looking at the coherence of all the evidence, including the observational epidemiology, the lab studies, the mechanistic studies, you begin to see a picture and get more clarity.”

One way alcohol may lead to cancer is because the body metabolizes it into acetaldehyde, which causes changes and mutations in DNA, Dr. Gapstur said. The formation of acetaldehyde starts when alcohol comes in contact with bacteria in the mouth, which may explain the link between alcohol and cancers of the throat, voice box and esophagus, she suggested.

Dr. Anne McTiernan, a scientist at the Fred Hutchinson Cancer Research Center who was an author of one of the earlier reports on alcohol and breast cancer, said she was pleased that oncologists were focusing on alcohol.

“That puts some weight behind this,” she said. It “shows they’re serious about it and willing to put their name on the line for changes in policy, and willing to say that even small amounts of alcohol can increase the risks of some cancers to a small degree.”